So I emailed a completed assignment to one of my professors this morning, and I just received the following response: "Unfortunately, I cannot give you credit for your paper, as it was submitted after the due date. Your paper was to be completed BY March 4. This means that it needed to be submitted at 11:59pm on March 3 at the latest." He went on to tell me that it shouldn't be a big deal because the paper is only a small part of the overall grade, but that I should pay more attention to due dates in the future.
I guess he's technically correct about the distinction between "by" and "on," but that really strikes me as unnecessarily confusing. I've literally never seen a due date for anything listed as the day before which the assignment has to be submitted.
Am I wrong, here? If you see "due by (X date)," do you assume that you can submit the thing on X date?